App: use forward declaration to reduce compile time

src/App/DocumentObject.cpp

@@ -35,6 +35,7 @@
 #include "DocumentObjectExtension.h"
 #include "DocumentObjectGroup.h"
 #include "GeoFeatureGroupExtension.h"
+#include "ObjectIdentifier.h"
 #include "PropertyExpressionEngine.h"
 #include "PropertyLinks.h"
 

src/App/PropertyExpressionEngine.h

@@ -28,7 +28,7 @@
 #include <boost_signals2.hpp>
 #include <boost_graph_adjacency_list.hpp>
 #include <boost/graph/topological_sort.hpp>
-#include <App/Expression.h>
+#include <App/PropertyLinks.h>
 #include <set>
 
 namespace Base {
@@ -42,6 +42,7 @@ class DocumentObject;
 class DocumentObjectExecReturn;
 class ObjectIdentifier;
 class Expression;
+using ExpressionPtr = std::unique_ptr<Expression>;
 
 class AppExport PropertyExpressionContainer : public App::PropertyXLinkContainer
 {

src/App/PropertyLinks.cpp

@@ -38,6 +38,7 @@
 #include "Document.h"
 #include "DocumentObject.h"
 #include "DocumentObjectPy.h"
+#include "ObjectIdentifier.h"
 
 
 FC_LOG_LEVEL_INIT("PropertyLinks",true,true)

src/Gui/CommandDoc.cpp

@@ -36,6 +36,7 @@
 
 #include <App/AutoTransaction.h>
 #include <App/DocumentObject.h>
+#include <App/Expression.h>
 #include <App/GeoFeature.h>
 #include <Base/Exception.h>
 #include <Base/FileInfo.h>

src/Gui/DlgPropertyLink.cpp

@@ -39,6 +39,7 @@
 #include <App/DocumentObject.h>
 #include <App/GeoFeature.h>
 #include <App/DocumentObserver.h>
+#include <App/ObjectIdentifier.h>
 #include <App/PropertyPythonObject.h>
 
 #include "Document.h"

src/Gui/propertyeditor/PropertyItem.cpp

@@ -39,6 +39,7 @@
 
 #include <App/Document.h>
 #include <App/DocumentObject.h>
+#include <App/Expression.h>
 #include <App/PropertyGeo.h>
 #include <App/PropertyFile.h>
 #include <App/PropertyUnits.h>

src/Mod/Part/Gui/DlgFilletEdges.h

@@ -30,6 +30,9 @@
 #include <QStandardItemModel>
 #include <QItemDelegate>
 
+namespace Base {
+    class Quantity;
+}
 namespace Part { 
     class FilletBase;
     class Fillet;

src/Mod/Sketcher/App/SketchObject.cpp

@@ -65,7 +65,10 @@
 
 #include <App/Application.h>
 #include <App/Document.h>
+#include <App/Expression.h>
 #include <App/FeaturePythonPyImp.h>
+#include <App/ObjectIdentifier.h>
+#include <App/OriginFeature.h>
 #include <App/Part.h>
 #include <Base/Writer.h>
 #include <Base/Reader.h>
@@ -73,8 +76,6 @@
 #include <Base/Console.h>
 #include <Base/Vector3D.h>
 
-#include <App/OriginFeature.h>
-
 #include <Mod/Part/App/Geometry.h>
 #include <Mod/Part/App/DatumFeature.h>
 #include <Mod/Part/App/BodyBase.h>

src/Mod/Sketcher/Gui/TaskSketcherConstraints.cpp

@@ -48,6 +48,7 @@
 #include <Base/Tools.h>
 #include <App/Application.h>
 #include <App/Document.h>
+#include <App/Expression.h>
 #include <Gui/Application.h>
 #include <Gui/Document.h>
 #include <Gui/Selection.h>